NIST Property Data Summaries Titanium Diboride (TiB2)
R G. Munro
Nearly fully dense polycrystalline TiB2 can be produced by a variety of processing methods, including sintering, hot pressing, hot isostatic pressing, microwave sintering, and dynamic compaction. The relatively strong covalent bonding of the constituents, however, results in low selfdiffusion rates. Consequently, given also a high melting point of (3225 20) C, pressureless sintering of TiB2 requires a relatively high sintering temperature, on the order of 2000 C. Unfortunately, grain growth is also accelerated by the higher temperature, and the anisotropy of the hexagonal grain structure results in deleterious internal stresses and the onset of spontaneous microcracking during cooling. Grain growth can limited and densification enhanced by the use of sintering aids such as Cr, CrB2, C, Ni, NiB, and Fe. The solubility of TiB2 in liquid Ni and Fe appears to be especially useful in this regard. In such cases, the mass fraction of the sintering aid in the specimen may range from 1% to 10 % while the sintering temperature may be reduced to the range of 1700 C to 1800 C for sintering times on the order of 1 h. Successful hot pressing with Ni additives can be achieved with a hot pressing temperature as low as 1425 C with a sintering time of 2 h to 8 h.The data presented here were derived from reported values for a narrowly defined material specification. Using trend analysis property relations, and interpolation methods, the selfconsistent trend values for the properties of polycrystalline TiB2 were determined for a mass fraction of TiB2 of at least 98 %, a density of (4.5 0.1) g/cm3, and a mean grain size of (9 1) m.
NIST Property Data Summaries Titanium Diboride (TiB<sub>2</sub>)